VHF radar and MF/HF dynasonde observations during Polar Mesosphere Summer Echoes conditions at EISCAT

The EISCAT VHF radar (224 MHz) and the EISCAT dynasonde (1–10 MHz) were operated simultaneously during a Polar Mesosphere Summer Echoes (PMSE) event on 22 June 1994. We investigate the echo characteristics revealed by these two instruments. The antenna of the VHF radar was set 10° off-zenith to the north for both transmission and receiving, while the dynasonde was operated with vertical beam to record ionograms every 3 minutes. The Height-Time-Intensity (HTI) variation of the VHF radar PMSE is studied, which is characterized layered structures. The intensity profiles are quite intermittent which show similarity to those data recorded by the dynasonde. To study the ionospheric condition with the dynasonde, the quantities of signal-to-noise ratio, echo frequency, echo polarization, echolocation, and Doppler velocity are investigated. Variations in the quantities demonstrate that during the PMSE conditions, echoes of the dynasonde are mainly attributed by reflection of many small irregularities within the observed ionospheric volume.